quadrature decoding brainstorming

encoder.c

uint8_t encoder_state;

int32_t position;


encoder ()
{
  encoder_state = encoder_state<<2 | PB1<<1 | PB2;
  
  switch (encoder_state & 0x0f)
  {
    // one direction
    case 0b0001:
    case 0b0111:
    case 0b1110:
      // break;  .. when only full cycles shall be counted
    case 0b1000:
      ++position;
      break;   
      
    // other direction
    case 0b0010:
    case 0b1011:
    case 0b1101:
      // break; 
    case 0b0100:
      --position;
      break;
      
    // no transition (when polling and not interrupt driven)
    case 0b0000:
    case 0b0101:
    case 0b1010:
    case 0b1111:
      // maybe: encoder_state >>= 2; // drop this transition
      break;

    // the errorneous transitions  
    //case 0b0110:
    //case 0b1001:
    //case 0b1100:
    //case 0b0011:
    default:
      /* handle error */
      //note that the higher bits (encoder_state & 0xfc) contain history of previous 3 moves
      
      break;
  }

}